Adds psr/http-message support

What's Changed

• Add Support for psr/http-message v2 by @donatj in #22
• Test in PHP 8.2 by @donatj in #21

Dependency Update

• Update php-mock/php-mock-phpunit requirement from ^2.6 to ^2.7 by @dependabot in #19

Full Changelog: v0.4.1...v0.5.0